Light emitting module and the method of the producing the same

ABSTRACT

The optical module  10  of the present invention comprises a semiconductor optical device  14,  a package  12  containing the semiconductor device, and lead terminals  22.  The package  12  comprises a bottom member  34  and a side member  36.  The bottom member contains a device mounting surface S 2,  the side member mounting surface S 3,  and a lead terminal joining surface S 1.  The optical semiconductor device  14  is mounted on the device mounting surface S 2  and lead terminals are joined to the lead terminal joining surface S 1.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to a light emitting module and the methodof the producing the module.

[0003] 2. Related prior art

[0004] A typical light emitting module comprises a light emittingsemiconductor device such as a laser diode and a package containing thedevice therein. The package has a rectangle shape, which is called abutterfly package, and provides lead terminals. Electrical signals bywhich the semiconductor device is driven are lead through leadterminals.

[0005] In the conventional module, a sub-assembly in which the lightemitting device and some optical members are assembled beforehand isinstalled into the butterfly package, a bottom member and a side memberof the package are rigidly put together. It is necessary to secure anenough space to handle tools for installing the sub-assembly in thepackage and for electrically connecting between the sub-assembly andlead terminals, which is an obstacle to the small-sized module.

[0006] In the conventional package, lead terminals are fixed to the sidemember of the package; the level of lead terminals is the same as thatof the light emitting device. When the module is surface mounted to themotherboard, the lead must be elongated to bend downwardly. Theelongated lead coupled with the large package results on the longer pathlength from the lead terminal, the high frequency signal input thereon,to the light emitting device, which brings the deterioration of the highfrequency performance of the module.

SUMMARY OF THE INVENTION

[0007] The object of the present invention is to provide an advancedoptical module and the manufacturing method of the same, which enables asurface mount configuration without causing the inferiority of the highfrequency performance.

[0008] To realize the object, the module according to the presentinvention comprises an optical semiconductor device, a packagecontaining the emitting device therein, and lead-terminals. The packagecomprises a bottom member and a side member. The bottom member may havea device mounting surface, a side member mounting surface surroundingthe device mount surface therearound, and a lead forming surfacesurrounding the side member mounting surface. The device mountingsurface mounts the semiconductor device thereon, and the lead terminalscontact the lead forming surface thereto.

[0009] In the present module, it is enable to bond the side member tothe bottom member after mounting the semiconductor device on the devicemount surface and electrically connecting the device to peripheralcomponents. Therefore, the side member is not an obstacle in installingthe semiconductor device and wiring the device to other devices. Hence,this leads a small sized package.

[0010] The configuration of lead terminal that attached to the bottommember of the package shorten the length of the terminal compared withthe conventional configuration when the module is surface mounted on amotherboard. Moreover, the size of the module itself is to be small sizeas mentioned. Therefore, the path from the tip of the terminal, the highfrequency signal input therein, to the semiconductor device isshortened, thus prevents the deterioration of the high frequencyperformance of the module.

[0011] It is favorable that the level of the device mounting surface beabove that of the lead forming surface, because the alignment betweenthe semiconductor device and an optical fiber, the optical signaltransmits therethrough, is facilitated.

[0012] It is also favorable that the level of the side member mountingsurface is between the lead forming surface and the device mountingsurface. The attachment of the side member of the package to the bottommember is simple.

[0013] It is favorable to fix the side member to the bottom member aftermounting the semiconductor device on the device mounting surface andperforming the wire bonding the semiconductor device to the peripheralcircuit. This assembling process makes it possible to eliminate theextra space within the package and to shrink the size of the package.The path length from the lead terminal, the high frequency signal inputthereto, to the peripheral circuit is shortened, thus prevents thedeterioration of the high frequency performance of the module.

BRIEF DESCRIPTION OF DRAWINGS

[0014]FIG. 1 is an exploded view of a module according to the presentinvention, FIG. 2 is a partial cut away view of the module.

DETAILED DESCRIPTION OF THE INVENTION

[0015] The favorable embodiments of the configuration and themanufacturing method of the optical module will be described inreferring to drawings. In the description, elements identical to eachother will be referred to with numerals identical to each other withouttheir overlapping explanations.

[0016]FIG. 1 is exploded view and FIG. 2 shows a partial cut away viewof the present optical module. As shown in FIG. 1 and FIG. 2, theoptical module 10 provides a package 12, an optical semiconductor device14, a peripheral circuit 16 for the semiconductor device, a lightreceiving device 18, a lens 20, a plurality of lead terminals 22, aferrule 26 for containing an optical fiber 24 therein, a sleeve 28 forinserting the ferrule 26 thereinto, a sleeve holder 30 for securing thesleeve 28 and a connector 32.

[0017] The package 12 comprises a bottom member 34, a side member 36 anda top member 38, respective members 34 to 38 are formed independently.The bottom member 34 provides a package substrate 40, a wiring substrate42 arranged on the upper surface of the package substrate 40, and aninsulating member 44 on the package substrate 40, the insulating member44 surrounds the wiring substrate 42.

[0018] The package substrate 40 is made of a material with good athermal conductivity and an insulating characteristic, the shape ofwhich is rectangle and board form. Aluminum nitride is suitable for thepackage substrate. The upper surface of the package substrate 40provides conductive wiring 46 thereon to conduct an electrical signalinput into lead terminals 22 to the peripheral circuit 16. A peripheralportion surrounding the insulating member 44 on the upper surface of thepackage substrate 40 provides a lead forming surface S1.

[0019] The wiring substrate 42 is a multi-layered substrate, which laysthin films of insulating materials, such as Aluminum nitride andAluminum ceramics. The substrate 42 is rectangle that is one sizesmaller than the package substrate 40.

[0020] The bottom surface of the wiring substrate 42 directly contactswith the upper surface of the package substrate 40. The upper surface ofthe wiring substrate 42 provides a device mounting surface S2, thesemiconductor device 14 and the peripheral circuit 16 is mountedthereon. A plurality of via holes 48 is bored through the upper surfaceand the bottom surface of the wiring substrate in the neighbor of thedevice mounting surface S2. Conductive metals are plugged within viaholes 48, which form conductive member 50. The conductive member 50connects the conductive wiring 46.

[0021] The insulating member 44 is made of an Aluminum nitride (AlN) orAluminum ceramics. The member 44 is mounted on the package substrate 40and surrounds the wiring substrate 42 therein. The upper surface of theinsulating member 44 provides a side member mounting surface S3; theside member 36 of the package 12 is placed thereon. In the presentembodiment, the insulating member 44 and the wiring substrate 42 areindependent to each other. It is favorable to form integrally theinsulating member and the wiring substrate 42.

[0022] Thus forms the bottom member 34 of the package 12 by mounting thewiring substrate 42 and the insulating member 44 onto the packagesubstrate 40. In such configuration of the bottom member 34, the uppersurface of the wiring substrate 42 positions above the upper surface ofthe package substrate 40 containing the lead forming surface S1. Theupper surface of the insulating member, which provides the side membermounting surface S3, positions between the upper surface of the packagesubstrate 40 and the upper surface of the wiring substrate 42.

[0023] The side member 36 is made of a metal, such as Kovar. The sidemember comprises a pair of side walls 36 a, which extends along an axisX shown in FIG. 2, a front end wall 36 b and a back end wall 36 c bothintersecting the axis X. The front end wall 36 b provides a bore 52 topass light emitted from the semiconductor device 14. Within the bore, aglass sheet 54 is inserted to seal the package 12 hermetically. The sidemember 36 is mounted on the insulating member 44 in the state that theinner side of the side member 36 contacts the side surface of the wiringsubstrate 42.

[0024] The top member 38 is also made of metals, such as Kovar. The topmember seals the opening of the side member 36.

[0025] The semiconductor device 14 is mounted on the upper surface ofthe wiring substrate 42 through a sub-mount 56. The device 14 has alight emitting surface 14 a and a light reflecting surface 14 b. Thedevice 14 is driven by the peripheral circuit 16 and emits lightmodulated by a signal output from the driving circuit 14 from the lightemitting surface 14 a. It is favorable to use a semiconductor laser asthe device 14. The peripheral circuit 16 is placed in a positionopposing to the light reflecting surface of the device 14 and rightclose to the device 14 on the wiring substrate 42. The peripheralcircuit 16 receives the signal input at lead terminals 22, amplifies theinput signal and generates the driving signal of the semiconductordevice 14. The driving signal is conducted to the semiconductor opticaldevice 14.

[0026] The light receiving device 18 is fixed onto a side surface of aholder element 58 and the wiring substrate 42 mounts the holder element58 thereon. The holder 58 is placed so as to insert the peripheralcircuit 16 by the semiconductor device 14 therebetween. A lightreceiving surface of the light receiving device 18 is optically coupledto the light reflecting surface 14 b of the semiconductor device 14. Thelight receiving device 18 monitors a light emitting behavior of thesemiconductor device 14. A device to generate a photosensitive current,such as a PIN photo diode is favorable for the receiving device 18.

[0027] The lens 20 is mounted on the wiring substrate so as to insertthe semiconductor device 14 by the peripheral circuit 16 therebetween.The lens is planed off to form a parallel surface of the top and thebottom portion of the ball lens. Since the bottom surface of the lens islevel, it is enable to mount directly on the wiring substrate 42. Thelens 20 is placed after aligning the optical axis as adhering the topsurface of the lens 20 by the manipulator. In the case that the surfaceof the lens 20 is spherical, misplacement may occur when the lens 20 isfixed on the substrate 42. By shaping the top surface and the bottomsurface of the lens 20 into level, the misplacement of the lens 20 canbe evaded because it is enable to adhere the top surface of the lens 20as keeping the bottom surface of the lens 20 and the top upper surfaceof the wiring substrate 42 in parallel.

[0028] The ferrule 26 is made of Zirconia ceramics and optical fiber 24is inserted thereinto. The ferrule 26 is squeezed into the sleeve 28made of metal. The holder 30 holds sleeve 28. The sleeve holder 30 isfixed on the outer surface of the front-end wall 36 b of the side memberat the location where the bore 52 is provided. The optical fiber 24 andthe lens 20 are optical aligned to each other through the ferrule 26,the sleeve 28 and the sleeve holder 30. Therefore, the light emittingsurface 14 a of the semiconductor device 14 and a tip 24 of the fiber 24are optically aligned through the lens 20.

[0029] As shown in FIG. 2, the optical fiber 24, the bore 52, the glasssheet 54, the lens 20, the semiconductor device 14, the peripheralcircuit 16 and the light receiving device are aligned along the axis Xin this order. The semiconductor device 14, the peripheral circuit 16,the lens 20 and the light receiving device 18 are air-tightly sealedwithin the package 12, while the optical fiber 24, the ferrule 26, thesleeve 28 and the sleeve holder 30 are fixed out of the package 12.

[0030] The connector 32 covers the ferrule 26, sleeve 28 and the sleeveholder 30 therein. The optical module 10 is able to couple to theanother optical element through the connector 32.

[0031] Lead terminals 22 are fixed on the lead forming surface S1surrounding the insulating member 44 on the package substrate 40. Leadterminals 22 are connected to bonding pads4 46 formed on the leadforming surface. Lead terminals 22 are bent downward to enable thesurface mount on a motherboard (not shown in figures). By thisconfiguration, a high frequency signal from the mother board istransmitted to the peripheral circuit 16 through lead terminals 22, theconductive wiring 46, the conducting member 50 within via holes 48 andbonding wires 60. Once transmitted signal to the peripheral circuit 16is amplified and applied to the semiconductor device 14. The signallight modulated by thus applied to the semiconductor device 14 isemitted from the light emitting surface 14 a. The light from thesemiconductor device 14 is condensed by the lens 20, passing through theglass sheet 54 and the bore 52 in the side member 36 of the package 12,and enters into the optical fiber 24 through the tip 24 a.

[0032] Next is an explanation of the manufacturing method of the opticalmodule 10.

[0033] The first step of the assembling process is to place the wiringsubstrate 42 onto the upper surface of the package substrate 40.Meanwhile, it is aligned between the conductive wiring 46 on the uppersurface of the package substrate 40 and the conductive member 50 withinvia hole 50 of the wiring substrate. Next, the insulating member 44 isplaced in the periphery on the package substrate 40. In the case thatthe wiring substrate 42 and the insulating member are made from onebody, it is enable to simplify the manufacturing process only bymounting the wiring substrate 42 onto the package substrate 40.

[0034] Next, lead terminals 22 bent downward are connected to bondingpads on the lead forming surface S1. It is able to fix lead terminalsonto the surface S1 before placing the wiring substrate 42 onto thepackage substrate 40. By installing lead terminals at the early stage ofthe manufacturing, it will be able to couple the optical fiber 24 andthe device 14 as operating the device 14.

[0035] After fixing the wiring substrate 42, the light receiving device18, the peripheral circuit 16, the semiconductor device 14, and the lens20 are mounted on the predetermined position of the wiring substrate 42.The semiconductor device 14 is mounted through the sub-mount 56. Thelight receiving device 18 is fixed onto the side surface of the holder58, and the holder 58 is mount on the wiring substrate 42. Meanwhile,the receiving device 18, the peripheral circuit 16, the semiconductordevice 14, and the lens 20 are aligned along the predetermined axis X inthis order.

[0036] After then, the conductive member 50 within via holes 48 isconnected to the peripheral circuit 16, and the peripheral circuit 16 isconnected to the semiconductor device 14 by wiring, respectively.

[0037] Next, the side member 36 is installed onto the side membermounting surface S3 on the insulating member 44. The sleeve holder 30,the ferrule 26 is secured therein through the sleeve 28, is fixed to theposition where the bore 52 is formed. In this step, the position of thesleeve holder is adjusted so as to couple optically the light emittingsurface 14 a of the semiconductor device 14 to the tip 24 a of theoptical fiber 24 through the lens 20. As explained previously, lightfrom the semiconductor device 14 is practically entered into the tip 24a of the optical fiber 24 and monitors output light from the other tipof the fiber 24. The position of the sleeve holder 30 is adjusted so asto maximize the optical power monitored at the other end of the fiber24. After fixing the sleeve holder 30, the connector 32 is attached tocover the sleeve holder 30, the sleeve 28 and the ferrule 26.

[0038] Finally, the opening of the side member 36 is sealed by the topmember 38, which hermetically seals the optical model 10.

[0039] The optical module of the present embodiment, the package 12 isformed separately by the bottom member and the side member, whichenables the fixing of the side member 36 to the bottom member 34 aftermounting optical devices, such as the semiconductor device 14, in thedevice mounting surface S2 and wiring to devices mounted thereon.Therefore, the side member 36 is not an obstacle when optical elements,such as the semiconductor device 14, are mounted on the bottom member 34and the wire bonding between such devices are performed, which removesthe extra space within the package, hence results on the small-sizedoptical module.

[0040] Moreover, lead terminals 22 are connected on the lead formingsurface S1 on the bottom member 34, which shorten the length of leadterminal at the surface mount configuration compared with theconventional configuration in which lead terminals are connected to theside member of the package. The length from the tip of the leadterminal, to which a high frequency driving signal is input, to thesemiconductor device 14 is able to shorten. This prevents thedeterioration of the high frequency performance of the module.

[0041] In the present optical module 10, since the device mountingsurface S2 positions above the lead forming surface S1, the opticalalignment of optical elements mounted in the surface S2 is simplified.

[0042] Furthermore, since the wiring substrate 42 provides plurality ofvia holes 48, the conducting member 50 is plugged therein to connect theconductive wiring in the package substrate to the driving circuit on thesurface S2, it enables the path from the lead terminal 22 to theperipheral circuit 16 to be short.

[0043] The peripheral circuit 16 is mounted adjacent the semiconductordevice 14 on the device mounting surface S2. This results on theimprovement of the high frequency performance of the module.

[0044] From the invention thus described, it will be obvious that theinvention may be varied in many ways. It is appropriate to vary theconfiguration of the module. One example is that the configuration ofthe present invention may be applicable to the light receiving module,although the specification describes mainly the light emitting module. Aphoto diode PD and a pre-amplifier circuit are used in the lightreceiving module as an optical semiconductor device 14 and a peripheralcircuit 16, respectively. The lens 20 condenses light emitted from thetip of the optical fiber 24 a to the light receiving surface of the PD14.

[0045] Even in the receiving module, the configuration of the presentpackage, in which the side member is independent of the bottom memberand the optical components are mounted on the bottom member without theside member, enables the optical alignment of such optical componentsand the electrical wiring to be simple. Moreover, to provide the leadterminal in the package substrate prevents the deterioration of the highfrequency performance of the module.

[0046] Such variations are not to be regarded as a departure from thespirit and scope of the invention, and all such modifications as wouldbe obvious to one skilled in the art are intended for inclusion withinthe scope of the following claims.

What is claimed is:
 1. An optical module comprising: an opticalsemiconductor device; a package accommodating the optical semiconductordevice therein, said package comprises a bottom member and a sidemember; and at least a lead terminal, wherein said bottom memberincludes a device mounting surface for mounting said semiconductordevice thereon, a side member mounting surface for surrounding thedevice mounting surface therearound, and a lead forming surface forjoining said at least a lead terminal thereto and for surrounding saidside member mounting surface therearound.
 2. The optical moduleaccording to the claim 1, wherein a level of said device mountingsurface is above said lead forming surface.
 3. The optical moduleaccording to the claim 1, wherein a level of said side member mountingsurface is between said device mounting surface and said lead formingsurface.
 4. The optical module according to the claim 1, wherein saidbottom member further includes a package substrate having a firstsurface, a conductive wiring being formed thereon, and a wiringsubstrate having a first surface and a second surface, said firstsurface of said package substrate provides said wiring substrate thereonso as to contact said first surface of said package substrate to saidfirst surface of said wiring substrate, wherein said first substrate ofsaid package substrate includes said lead forming surface and saidsecond surface of said wiring substrate includes said device mountingsurface.
 5. The optical module according to the claim 4, furtherincludes a via hole provided in said wiring substrate, a conductivemetal being plugged in said via hole to connect said first surface ofsaid package substrate to said device mounting surface of said wiringsubstrate.
 6. The module according to the claim 4, further includes aninsulating member having first surface and a second surface, said firstsurface contacting to said first surface of said package substrate andsaid second surface including said side member mounting surface.
 7. Themodule according to the claim 4, wherein said wiring substrate is madeof multi-layered AlN.
 8. The module according to the claim 1, whereinsaid semiconductor device is a laser diode.
 9. The module according tothe claim 1, wherein said semiconductor device is a photo diode.
 10. Themodule according to the claim 1, further includes a peripheral circuitfor activating said semiconductor device, said device mounting surfaceproviding said peripheral circuit thereon.
 11. The module according tothe claim 1, further includes a lens for condensing light for opticallycoupling said semiconductor device to a tip of an optical fiber, saiddevice mounting surface mounting said lens thereon.
 12. The moduleaccording to the claim 1, further includes a bore provided on said sidemember for passing light.
 13. The module according to claim 9, furtherincludes a holder fixed so as to surround said bore for holding aferrule inserting said optical fiber thereinto, said semiconductordevice being coupled to said tip of said optical fiber through saidbore.
 14. An optical module comprising: a light emitting semiconductordevice; a peripheral circuit for driving said semiconductor device; alens for condensing light emitted from a light emitting surface of saidsemiconductor device; and a package for securing said semiconductordevice, said peripheral circuit, said lens, and said holder therein,said package comprising a side member, a bottom member independent ofsaid side member, and at leas a lead terminal, wherein said bottommember includes a device mounting surface for mounting saidsemiconductor device, said driving circuit, and said lens thereon, aside member mounting surface surrounding said device mounting surfacetherearround, and a lead forming surface for joining said at leas a leadterminal thereto, said lead forming surface surrounding said side membermounting surface there around.
 15. The module according to the claim 14,further includes a bore provided on said side member for passing lightfrom a light emitting surface of said semiconductor device, and a holderfixed so as to surround said bore for holding a ferrule inserting anoptical fiber thereinto, said light emitting surface of saidsemiconductor device being coupled to a tip of said optical fiberthrough said lens and said bore.